Dust filter



March 2, 1954 R. B. EVANS 2,670,809

DUST FILTER Filed April 25, 1951 INVENTOR.

333521- B- Ema 5 Patented Mar. 2, 1954 UNITED STATES PATENT OFFICE DUST FILTER Robert B. Evans, Plum Township, Pa., assignor to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania Application April 25, 1951, Serial No. 222,777

8 Claims. (01. 183-44) This invention relates to air filters, and more particularly to those adapted to be supported by a face piece and containing sheet filtering material for filtering out dust particles.

The filter disclosed herein is especially suitable for use with a face piece such as shown in my co-pending patent application, Serial No. 219,274, filed April 4, 1951.

It is among the objects of this invention to provide an air filter which has a simple and inexpensive construction, which has a large fiiltering area for its size, and which contains a sheet of filtering material that can be quickly and easily clamped in place or removed from the body of the filter for replacement.

In accordance with this invention, the case of the filter has a back Wall provided with an air outlet, and the front of the case is provided with a large inlet opening. The area of the inlet opening is increased by continuing it around one end of the case and part way along the back of the case toward its outlet. A removable perforated cover for the inlet opening has one end likewise extending around the end of the case. A sheet of filtering material covers the inlet opening and is pressed into sealing engagement with the case by means of the cover. The open end of the case may be provided with a cross bar around which the sheet of filtering material extends. The opposite sides of the case preferably are provided with flanges to keep the sheet of filtering material and the cover from shifting laterally.

Ihe preferred embodiment of the invention is illustrated in the accompanying drawings, in which Fig. l is a front view of the filter; Fig. 2 is a back view thereof; Fig. 3 is a side view; Fig. 4 is a vertical section taken on the line IV-IV of Fig. 1; Fig. 5 is a side view of the cover alone; Fig. 6 is a front view of the case with'the cover and half of the filter sheet removed; and Fig. 7 is a back view of the case similar to the preceding figure.

Referring to Figs. 4, 5 and 6 of the drawings, the case has a pair of laterally spaced side walls I that are integrally connected at their upper ends by means of an end wall 2 and a back wall 3 that extends about half way down the case. The back wall is provided with an opening 4 which serves as an air outlet and a means by which the filter can be connected to the lower front portion of a face piece in the manner shown in my copending patent application mentioned above. The lower ends of the sides of the case are connected by a thin cross bar 5. The outer edge of each VII is curved around cross bar 5.

2 side wall is surrounded by a flange 6, except where the back Wall is located. The side walls of the case preferably converge upward to form an upwardly tapered case that will obstruct the wearers vision as little as possible.

The large open areas between the front edges of the side walls and between the rear edges of the side walls below the back wall form a large inlet opening 8 for the filter. This inlet opening is covered by a perforated cover 9 that extends from the top of the case down the front, around the bottom, and up the back far enough to overlap the back wall a short distance. The cover is tapered to conform to the shape of the case. and the spaced front and back portions of the cover are substantially parallel to each other. The upper end of thecover extends only part way across the upper end wall of the case and is provided on its lower surface with a rib 10 that projects down into a groove II in the case end wall. The interengaging detents thus formed hold the cover in place. The cover can be removed by springing the rib out of the groove and then sliding the cover down the case.

Filtering is accomplished with this device by means of a flexible sheet 13 of filtering material of any well known composition between the cover and the case. The opposite end portions of the sheet are tapered in the same manner as the cover so that they will fit between the front and rear side flanges of the case. The sheet is of such length that one end of it will overlap the front of the upper end wall of the case, and the opposite end of the sheet will overlap the lower end of the case back wall. The edges of the sheet overlie the front and rear surfaces of the case side walls, and the lower portion of the sheet In applying the filter sheet to the case, it can be placed between the side flanges and slid upward until its edges engage them. Then, while the upper end of the sheet is held against the case end wall with the fingers, the lower portion of the sheet is wrapped around the, bottom of the case and up the back. The cover then is slipped up over the case from the bottom until the rib ID on its upper end springs into groove II to lock the cover in place. The cover fits tightly enough to press the marginal portions of the sheet tightly against the front and back and lower end of the case, thus forming a seal. Consequently, all air that passes through the filter case must first pass through the cover and filter sheet. Due to the large area of the inlet opening in the case, breathing resistance is reduced to a minimum for the small size of the case. When the breathing resistance starts to increase, thereby indicating that the filter sheet is becoming clogged by particles that it has removed from the air passing through it, it is a simple matter to remove the cover and sheet from the case and to apply a new sheet.

According to the provisions of the patent statutes, I have explained the'principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An air filter comprising a case having opposite ends with a back wall between them provided with an air outlet, the front of the 'case being provided with a large inlet opening, a removable perioratedcoverior said inletopening having two oppositeends with one endexten'ding around one'end of the caseandalongits back toward said'outlet, and a removable sheet of filtering material covering the inletiopening' and pressed into sealingengagementwith the case by said cover.

-2. Anair filter comprising a case having oppositeends with a back wallbetweenthem providedwith an air outlet, thefront of the case :1 being provided with alarge-inlet opening that continues around one oi -said ends and-part way along the back of the-case, a removable periorated cover for said inlet opening having one end-extending aroundsaidopen end of the case ;I-

and overthe portion of said opening in its back, and a removable sheet oi filtering material covering-the inletopening in 'the front and back of the case and pressed-into sealing engagement with the case by said cover.

3. An-air filter comprising acase-having op- "posite endswith aback wall between them provided with an'air outlet, the front of theca-se being provided with a large -inlet opening, a

removable perforated-elongated cover for said inlet opening having one end provided with a return bend to i provide spaced front and back portions, theback portion ofthe coverextending only partway up its front portion, said cover 'portions being adapted to be slipped over-one end of the case, and-a removable sheet of filtering material covering the inletopening--andpressed into sealing engagement with --'the ease a; around that opening" by means of-said cover.

"4. Anair filter comprising acase having -opposite'endswith aback wall-between them provided withan air outlet,--the-front of the-case "being provided with -a large inlet opening, a

removable perforated cover for said inlet opening lockingthe'cover on the case, and -a'removab'le sheetof filtering material covering the inlet opening and pressed into sealing engagement with the case by said-cover, said detent end of the cover being adapted to be sprung away from the case to unlock it therefrom.

5. An air filter comprising a case having opposite ends with a back wall between them provided with an air outlet, the front of the case being provided with a large inlet opening that continues around one of said ends and part way along the back of the case, a cross bar connecting the opposite sides of said open end of the case, a removable perforated cover for said inlet opening having one "end "portion extending around said cross bar and over the portion of said opening in the back of the case, and a re- -movable sheet of filtering material covering the front and back portions of the inlet opening and extending around the cross bar between it and the cover, the'oover pressing said sheet into sealing engagement'with the case around the inlet opening.

6. An air filter comprising a case having latby an end wall and a back wall, the back wall being shorter than the side walls and having anair outlet in it, a 'removable sheet of filtering material extending along the front and back of the case and around the end of the case opposite'the end wall, said sheet having its' ends overlapping said end and back walls and'having opposite side edges overlapping the-front and back of said side walls, and a removabl merforated cover pressing the ends and side edges of saidsheet against the case.

7. An air filter comprising a case having laterally spaced side walls connected atone end by an end wall and a back wall, the back-wallbcing provided with an air outlet, a removable elongated sheet of filtering material overlapping said end and back walls and the front ofsaid side walls, the case being provided with flanges projecting forward-from-the outer edges of its side walls, and a removable perforated cover disposed between said flanges and pressing the ends and side edges of said sheet-'against'the case.

8. An air filter comprising a'case having laterally spaced side'walls'connected at one end'by an end wall and a backwall and connected at the opposite endby a cross bar, the back'wall-being shorter than the side walls and having an air --outlet in it, the case alsobeingprovi'ded with flanges projecting'forward and backward and endwisefrom the outer'edges of its side'walls,

a removable sheetof-filtering material extending along the front andback of the case and around said cross bar, the sheet having ed'ges substantially engaging said flanges and having ends overlapping said end-and back walls, and

a removable perforated cover covering said sheet and pressing the ends and edges of the sheet against the case.

ROBERT 13;. EVANS.

References Cited in the file of this patent UNITED STAZUES PATENTS 

